1. Field of the Invention
The present invention relates generally to a shutter for use in a camera and, more particularly, to a camera shutter with plural shutter blades.
2. Description of the Related Art
One conventional focal plane shutter for use in a camera has a set of opening shutter blades and a set of closing shutter blades disposed behind base plates each of which is provided with a shutter opening. The two sets of shutter blades operate in sequence to alternately cover and uncover the shutter openings. The shutter blades of each set are supported by arms forming parallel links. The opening and closing shutter blades are actuated to open and close the shutter openings. Each shutter blade is normally made of a sheet of a metal or the like.
Since each shutter blade is made of a metal sheet, intimate contact between the successive shutter blades is poor. To maintain sufficient lightproofness, it has been necessary to crimp the blades in a direction to bring them into intimate contact with each other by a sophisticated machining or processing technique. If they are pressed against each other so that they make intimate contact with each other, a large frictional force acts on each at the start of actuation thereof. This makes the control of the exposure time inaccurate.
Accordingly, it is an object of the present invention to provide a camera shutter which can be fabricated without the need of sophisticated machining or processing techniques.
It is another object of the invention to provide a camera shutter having plural shutter blades capable of making contact with each other with improved intimateness to thereby provide enhanced lightproofness and which permits smooth and accurate control of exposure time.
A camera shutter with plural separate blades in accordance with the present invention has at least two base plates each provided with a shutter opening, the blades being mounted between the base plates, and a shutter driver mechanism for moving the blades between a first position at which the blades are extended and cover the shutter opening and a second position at which the blades are retracted and do not cover the shutter opening. A pushing member protrudes from either one of the base plates toward the shutter blades in the first position and pushes the shutter blades into intimate contact with each other. Prior to the start of an exposure, the pushing member stops pushing the shutter blades. In this structure, the shutter blades make contact with each other with improved intimateness, thus improving the lightproofness. Moreover, by releasing the pushing action of the pushing member prior to the start of an exposure, the shutter blades can move freely and thus the exposure time can be controlled smoothly and precisely.
Preferably, each of the shutter blades has a protrusion capable of bearing against the pushing member. Furthermore, the pushing member is preferably mounted within the shutter driver mechanism.